Control of storage protein metabolism in the cotyledons of germinating mung beans: role of endopeptidase.
نویسندگان
چکیده
The autodigestive proteolytic activity of extracts of cotyledons of mung beans (Phaseolus aureus Roxb.) increased 4- to 5-fold during germination. A similar increase was found in the ability of these extracts to digest added casein or mung bean globulins. The increase occurred after a 2-day lag during the next 2 to 3 days of germination and coincided with the period of rapid storage protein breakdown. To understand which enzyme(s) may be responsible for this increase in proteolytic activity, the hydrolytic activity of cotyledon extracts toward a number of synthetic substrates and proteins was measured. Germination was accompanied by a marked decline in leucine aminopeptidase, while carboxypeptidase increased about 50%. There were no dramatic changes in either alpha-mannosidase or N-acetyl-beta-glucosaminidase, enzymes which may be involved in the metabolism of the carbohydrate moieties of the reserve glycoproteins. The increase in general proteolytic activity was closely paralleled by a 10-fold increase in endopeptidase activity. This activity was inhibited by sulfhydryl reagents such as N-ethylmaleimide. Studies with inhibitors of proteolytic enzymes showed that reagents which blocked sulfhydryl groups also inhibited the rise in general proteolytic activity. Our results suggest that the appearance of a sulfhydryl-type endopeptidase activity is a necessary prerequisite for the rapid metabolism of the reserve proteins which accompanies germination.
منابع مشابه
Partial characterization of a protease inhibitor which inhibits the major endopeptidase present in the cotyledons of mung beans.
Germination of mung beans (Phaseolus aureus, Roxb.) is accompanied by an increase in the activity of the endopeptidase involved in storage protein metabolism. Enzyme activity in the cotyledons increases 25-fold during the first 5 days of germination. The cotyledons also contain inhibitory activity against the endopeptidase, and this inhibitory activity declines during germination, suggesting th...
متن کاملHistochemical and biochemical observations on storage protein metabolism and protein body autolysis in cotyledons of germinating mung beans.
Storage protein hydrolysis in the cotyledons of germinating mung beans (Phaseolus aureus Roxb.) was examined by histochemical techniques, and the autolytic capacity of isolated protein bodies was studied with biochemical methods. The localization of endopeptidase activity within the cotyledons was studied using an India ink-gelatin film technique. After 24 hours of imbibition, a low level of en...
متن کاملRegulation of reserve protein metabolism in the cotyledons of mung bean seedlings.
Seedling growth in mung beans (Phaseolus aureus, Roxb.) is accompanied by the metabolism of the reserve proteins, and the appearance in the cotyledons of a proteolytic enzyme with endopeptidase activity. Enzyme activity increases 25-fold during the first 5 days of growth. Cotyledon extracts prepared from seeds imbibed for 24 hr with water do not react with rabbit endopeptidase antiserum, which ...
متن کاملMetabolism of Inositol Phosphates: I. Phytase Synthesis during Germination in Cotyledons of Mung Beans, Phaseolus aureus.
The degradation of phytin in germinating mung bean seeds has been found to be associated with the increased activity of phytase in the cotyledon. In the differentiated embryo the increase of this activity is very low all throughout the growth periods studied. Phytase appears in the cotyledon during germination. No activity has been detected in the cotyledons of unsoaked seeds. Cycloheximide (10...
متن کاملA cysteine endopeptidase isolated from castor bean endosperm microbodies processes the glyoxysomal malate dehydrogenase precursor protein.
A plant cysteine endopeptidase with a molecular mass of 35 kD was purified from microbodies of germinating castor bean (Ricinus communis) endosperm by virtue of its capacity to specifically process the glyoxysomal malate dehydrogenase precursor protein to the mature subunit in vitro. Processing of the glyoxysomal malate dehydrogenase precursor occurs sequentially in three steps, the first inter...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Plant physiology
دوره 55 6 شماره
صفحات -
تاریخ انتشار 1975